POPULATION DYNAMICS AND FEEDING ECOLOGY OF SYNGNATHIDS INHABITING MEDITERRANEAN SEAGRASSES JULIA CASTRO FERNÁNDEZ-PACHECO TRABAJO FINAL DE MÁSTER BIOLOGÍA MARINA CURSO 2017/2018 TUTORES: JORGE TERRADOS MUÑOZ INÉS CASTEJÓN SILVO PABLO ARECHAVALA LÓPEZ FECHA DE DEFENSA: 2 DE JULIO DE 2018 - 1 - El Dr. Jorge Terrados Munóz, la Dra. Inés Castejón Silvo y el Dr. Pablo Arechavala López, investigadores del Instituto Mediterráneo de Estudios Avanzados (IMEDEA –CSIC/UIB), y co-tutores del Trabajo de Fin de Máster de la alumna Julia Castro Fernández-Pacheco (DNI: 51489996B ), HACEN CONSTAR: Que la alumna ha realizado satisfactoriamente su Trabajo de Fin de Máster, el cual está finalizado, evaluado y listo para su presentación y defensa en la convocatoria de Julio del 2018 en el Máster Interuniversitario en Biología Marina (Facultades de Biología de Galicia). Para que conste a efectos oportunos, firman en Esporles el 20 de Junio de 2018. Firmado digitalmente por CASTEJON SILVO Firmado por ARECHAVALA LOPEZ Firmado por TERRADOS INES - 51088754G PABLO - 09034684P el día MUÑOZ JORGE MIGUEL - Fecha: 2018.06.19 19/06/2018 con un certificado emitido por AC FNMT Usuarios 27431617T el día 16:03:16 +02'00' 20/06/2018 con un Dr. Jorge Terrados Muñoz Dra. Inés Castejón Silvo Dr. Pablo Arechavala López Firmado digitalmente por DOMINGUE DOMINGUEZ CONDE JESUS - 36046949S Nombre de reconocimiento (DN): Z CONDE c=ES, serialNumber=IDCES-36046949S, C/ MIQUEL MARQUÉS, 21 givenName=JESUS, 07190 ESPORLES JESUS - sn=DOMINGUEZ CONDE, ILLES BALEARS cn=DOMINGUEZ CONDE JESUS - TELF. 971 611 716 36046949S FAX 971 611 761 36046949S Fecha: 2018.06.22 12:24:51 +02'00' INDEX ABSTRACT ........................................................................................................................- 2 - INTRODUCTION .............................................................................................................. - 3 - OBJECTIVES .................................................................................................................... - 6 - MATERIALS AND METHODS ....................................................................................... - 6 - STUDY AREA AND SAMPLING DESIGN ................................................................. - 6 - PIPEFISH SAMPLING AND BIOMETRIES ............................................................... - 7 - PIPEFISH DISECCTIONS AND FEEDING HABITS ................................................ - 9 - EPIFAUNAL COMMUNITY ASSESSMENT ............................................................. - 9 - DATA ANALYSIS ........................................................................................................ - 11 - RESULTS .......................................................................................................................... - 12 - PIPEFISH POPULATIONS AND BIOMETRICS ...................................................... - 12 - FEEDING PREFERENCES ......................................................................................... - 17 - EPIFAUNAL COMMUNITY .......................................................................................- 20 - DISCUSSION .................................................................................................................... - 23 - CONCLUSIONS ............................................................................................................... - 27 - REFERENCES .................................................................................................................- 28 - ANNEX 1 ANNEX 2 - 1 - ABSTRACT Syngnathids are an emblematic, vulnerable and diverse group of the ichthyofauna associated to vegetated coastal and estuarine habitats (Campolmi et al., 1996). Seagrass meadows, where pipefish aspect and behavior makes them mimetic, provide shelter and food, and seem to be preferred habitats (Kendrick & Hyndes, 2005). Syngnathid population dynamics and feeding habits are still poorly known, especially in Mediterranean coastal waters (Vizzini and Mazzola, 2004). In order to understand syngnathid population trends and feeding ecology, pipefish assemblages from Posidonia oceanica and Cymodocea nodosa meadows in the Balearic Islands were studied. Pipefish were fished with an artisanal epibenthic trawl in both habitats, during warm and cold season. Associated epifauna (i.e. potential preys) was also sampled by scuba divers. Syngnathids were identified and measured (n=73). Head morphometry, stomach contents (n=43) and sexual maturity (n=22) were also studied. Epifauna samples were identified to main taxon. A total of 4 pipefish species were found: Syngnathus typhle, S. abaster, Nerophis ophidion and N. maculatus. Dominant species were S. abaster and S. typhle in C. nodosa and P. oceanica meadows respectively. Individuals captured in P. oceanica were significantly larger in size than those living in C. nodosa. Main prey items observed in stomach contents analyses were amphipods and copepods, which also were the most abundant taxa in epifaunal samples in both habitats, along with gastropods and polychaetes in P. oceanica. While standardized abundance of invertebrates was higher in C. nodosa, diversity of epifaunal communities was similar in both types of habitat. Although observed prey items were in accordance with epifaunal communities, variations were detected among pipefish species, sizes and habitats. Additionally, large individuals and some species (i.e. S. tyhple) have wider snouts and mouth openings, which allow them to catch and ingest larger preys such as decapods and even small teleost juveniles. Key words: Syngnathid, seagrass, feeding habits, population, Mediterranean. - 2 - INTRODUCTION Syngnathidae is a family of fish found in temperate and tropical seas across the world, which includes the seahorses, the pipefishes, the pipehorses, and seadragons (Figure 1). The name of this family is derived from Greek, “syn”, meaning "fused" or "together", and “gnathus”, meaning "jaws". This fused and toothless jaw trait is also something the entire family has in common, showing a particular feeding ecology (Leysen et al., 2011). They are considered secondary consumers with two specialized predatory strategies: sit and wait and/or slow search behavior (Tipton & Bell, 1988; Franzoi et al., 1993). They are characterized by an elongate tubular snout and could be considered as specialized suction feeders (Muller & Osse, 1984). The type and size of prey consumed by syngnathids varies depending on the size of the snout and the mouth opening, so they have obvious limitations while feeding (Lyons & Dunne, 2004). Figure 1. Fam. Syngnathidae: a) Seahorse Hippocampus guttulatus b) Pipefish Syngnathus tyhple c) Pipehorse Idiotropiscis lumnitzeri d) Seadragon Phycodurus eques. Syngnathids have some particular characteristics that collaborate to its vulnerability. First, male parental care (Vincent et al., 1995) where females pass the eggs from the oviduct into the ventral brood pouch developed by male, where the male inseminates them (Franzoi et al., 1993). However, some differences among genus can be found. For instance, within pipefish, the male brood pouch is typical in genus Syngnathus, while some other genus such as Nerophis have a simple ventral region where eggs are loosely attached without any protecting plates or covering membranes (Dawson, 1986; Monteiro et al., 2005). After fecundation, males carry and care the embryos throughout the gestation period until hatchling of the independent young (Berglund et al., 1986). - 3 - Vizzini & Mazzola (2004) reported that this reproductive behavior means a greater cost for males compared to females. Second, the investment in embryo protection structures that are among the most developed in fishes and the long embryonic development that lasts for one month (afterwards fully formed juveniles are released) (Monteiro et al., 2003; Silva et al., 2006). Behavior of newborn juveniles differ depending on the genus. While Syngnathus juveniles present a benthonic preference, in Nerophis they display a pelagic life phase (Monteiro et al., 2003; Silva et al., 2006). Third, the low number of eggs per couple and the couple fidelity habits. In this scenario juvenile survivorship is essential for species endurance, however juvenile mortality is commonly high due to predation, low mobility and habitat limitations. Recolonization of new areas will be typically very slow. Among syngnathids, pipefish are the most abundant group found in Mediterranean waters (Franzoi et al., 2010) (Figure 2), where 11 species have been reported according to the IUCN Red List of Threatened Species: Nerophis ophidion, N. maculatus, Syngnathus abaster, S. acus, S. typhle, S. phlegon, S. rostellatus, S. schmidti, S. tanaeionotus, S. tenuirostris and Minyichthys sentus. They are usually associated to seagrass meadows (Pita et al., 2002) and their feeding ecology is poorly known (Lyons & Dunne, 2004; Vizzini & Mazzola, 2004). Pipefish are an important component of the icthyofauna in vegetated coastal and estuarine lagoon habitats (Howard & Koehn, 1985; Campolmi et al., 1996). They mimic thin seagrass leaves in shape, color and orientation so they are protected from predators (Howard & Koehn, 1985; Fuller & Berglund, 1996). These highly specialized fishes are characterized by limited mobility due to the small size of their fins and the occurrence on their bodies of semi-rigid dermal plates that restrict flexibility. They select the habitats that best enable them to remain inconspicuous to predators, which points